SHA256 Class
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SHA256 Class

 

Computes the SHA256 hash for the input data.

Namespace:   System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)


[ComVisibleAttribute(true)]
public abstract class SHA256 : HashAlgorithm

NameDescription
System_CAPS_protmethodSHA256()

Initializes a new instance of SHA256.

NameDescription
System_CAPS_pubpropertyCanReuseTransform

Gets a value indicating whether the current transform can be reused.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyCanTransformMultipleBlocks

When overridden in a derived class, gets a value indicating whether multiple blocks can be transformed.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyHash

Gets the value of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyHashSize

Gets the size, in bits, of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyInputBlockSize

When overridden in a derived class, gets the input block size.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyOutputBlockSize

When overridden in a derived class, gets the output block size.(Inherited from HashAlgorithm.)

NameDescription
System_CAPS_pubmethodClear()

Releases all resources used by the HashAlgorithm class.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Byte[])

Computes the hash value for the specified byte array.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Byte[], Int32, Int32)

Computes the hash value for the specified region of the specified byte array.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Stream)

Computes the hash value for the specified Stream object.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodSystem_CAPS_staticCreate()

Creates an instance of the default implementation of SHA256.

System_CAPS_pubmethodSystem_CAPS_staticCreate(String)

Creates an instance of a specified implementation of SHA256.

System_CAPS_pubmethodDispose()

Releases all resources used by the current instance of the HashAlgorithm class.(Inherited from HashAlgorithm.)

System_CAPS_protmethodDispose(Boolean)

Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodHashCore(Byte[], Int32, Int32)

When overridden in a derived class, routes data written to the object into the hash algorithm for computing the hash.(Inherited from HashAlgorithm.)

System_CAPS_protmethodHashFinal()

When overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic stream object.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodInitialize()

Initializes an implementation of the HashAlgorithm class.(Inherited from HashAlgorithm.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubmethodTransformBlock(Byte[], Int32, Int32, Byte[], Int32)

Computes the hash value for the specified region of the input byte array and copies the specified region of the input byte array to the specified region of the output byte array.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodTransformFinalBlock(Byte[], Int32, Int32)

Computes the hash value for the specified region of the specified byte array.(Inherited from HashAlgorithm.)

NameDescription
System_CAPS_protfieldHashSizeValue

Represents the size, in bits, of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_protfieldHashValue

Represents the value of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_protfieldState

Represents the state of the hash computation.(Inherited from HashAlgorithm.)

The hash is used as a unique value of fixed size representing a large amount of data. Hashes of two sets of data should match if and only if the corresponding data also matches. Small changes to the data result in large unpredictable changes in the hash.

The hash size for the SHA256 algorithm is 256 bits.

This is an abstract class. The only implementation of this class is SHA256Managed.

The following example calculates the SHA-256 hash for all files in a directory.

using System;
using System.IO;
using System.Security.Cryptography;
using System.Windows.Forms;

public class HashDirectory
{

    [STAThreadAttribute]
    public static void Main(String[] args)
    {
        string directory = "";
        if (args.Length < 1)
        {
            FolderBrowserDialog fbd = new FolderBrowserDialog();
            DialogResult dr = fbd.ShowDialog();
            if (dr == DialogResult.OK)
                directory = fbd.SelectedPath;
            else
            {
                Console.WriteLine("No directory selected.");
                return;
            }
        }
        else
            directory = args[0];
        try
        {
            // Create a DirectoryInfo object representing the specified directory.
            DirectoryInfo dir = new DirectoryInfo(directory);
            // Get the FileInfo objects for every file in the directory.
            FileInfo[] files = dir.GetFiles();
            // Initialize a SHA256 hash object.
            SHA256 mySHA256 = SHA256Managed.Create();

            byte[] hashValue;
            // Compute and print the hash values for each file in directory.
            foreach (FileInfo fInfo in files)
            {
                // Create a fileStream for the file.
                FileStream fileStream = fInfo.Open(FileMode.Open);
                // Be sure it's positioned to the beginning of the stream.
                fileStream.Position = 0;
                // Compute the hash of the fileStream.
                hashValue = mySHA256.ComputeHash(fileStream);
                // Write the name of the file to the Console.
                Console.Write(fInfo.Name + ": ");
                // Write the hash value to the Console.
                PrintByteArray(hashValue);
                // Close the file.
                fileStream.Close();
            }
            return;
        }
        catch (DirectoryNotFoundException)
        {
            Console.WriteLine("Error: The directory specified could not be found.");
        }
        catch (IOException)
        {
            Console.WriteLine("Error: A file in the directory could not be accessed.");
        }
    }
    // Print the byte array in a readable format.
    public static void PrintByteArray(byte[] array)
    {
        int i;
        for (i = 0; i < array.Length; i++)
        {
            Console.Write(String.Format("{0:X2}", array[i]));
            if ((i % 4) == 3) Console.Write(" ");
        }
        Console.WriteLine();
    }
}

.NET Framework
Available since 1.1
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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